Our experimental model for the progression of the stages in vitro human cell carcinogenesis begins with the initiation of the microinsult and ends with the neoplastic growth of the transformed human epithelial cells in a nude mouse. We intend to use different in vitro indices to identify when the transformed human cell populations are progressing through the early, transitional and late stages of the transformation process. The requirement for activation or non-activation of the carcinogen and the specific or non-specific transport of the ultimate carcinogen into the genetic apparatus followed by initiation of the carcinogenic event will be part of this particular investigation. We suggest that the role of the "cell cycle accelerating agents" classified in the mammalian chemical carcinogenesis literature as promoters and anti-tumor agents do not act in the same manner in chemical carcinogen induced human cell carcinogenesis. That combining these compounds, with suspect chemical carcinogens during treatment of cell populations when in S do aid in concert in the expression of neoplastic transformation of low passage human diploid epithelial cell populations in vitro. We also propose that serially subpassaging the cell populations through soft agar does establish a population of transformed cells that can produce tumors in nude mice. We will correlate the in vitro indices of transformation for the early transitional and late stages of transformation, with changes in t-RNA methyl transferase activity and LETS proteins. These two indicies are reportedly associated with the neoplastic state, (Wainfan E. et al., Cancer Res. 38, 1852-1856, 1978; Chen, L., et al. Exptl. Cell Res. 106, 39-46, 1977.